Planovalgus foot deformity revisited

To the Editor:

I would like to thank the Journal for inviting me to respond to the article by Lynn T. Staheli titled “Planovalgus Foot Deformity: Current Status,” which appeared in the February 1999 issue. I want to say at the outset that I have the highest regard for the author, and do not question his integrity or sincerity. I believe that I have read all of his published articles, and consider his overall body of work to be a valuable contribution to the literature. The following commentary is not meant to be a point-by-point critique of the above-mentioned article but is an attempt to convey to the practice community that the body of literature on this topic does not provide a complete understanding of what constitutes “flat-foot” and what should be done about it. It is in this spirit that I offer the following points for readers to consider in evaluating the usefulness of Staheli’s article.

1) The stated purpose of this article is “to provide an objective review of current management of flatfoot in children” (p 94). An “objective” article presents two sides of an argument and evaluates the strengths and weaknesses of both sides. I do not find that this article attempts in any way to provide objective evidence; rather, the author presents a one-sided view and attempts to persuade the reader to accept the author’s opinions and biases. Certainly there is evidence for the author’s views; however, there are many weaknesses in the articles that he uses to support his opinions, and there is a body of evidence that would support the opposite viewpoint.

2) Staheli asserts that “during the past 3 decades, the natural history of flatfoot ... has been studied more completely” (p 94). I believe that this is an overstatement and implies that more is known about this condition than is actually the case. It would be more accurate to state that there have been some attempts in the last 20 years to try to better understand flatfoot. Staheli has done a very nice job of showing average arch height for children and adults; this could be used as a guide in the asymptomatic population [1]. However, it would be totally inappropriate to use this as a guide in symptomatic children or adults.

The opinions and assertions contained herein are the private views of the author and are not to be construed as official or as reflecting the views of the Department of Veterans Affairs, the Department of Defense, or any other representative or department of the US government.

Unfortunately, the term “flat foot” is just as poorly defined today as it was in 1888, when Royal Whitman published his initial thesis [2]. My opinion is that few people have improved on the criterion of Lovett and Cotton [3]: that the foot should be considered abnormally flat when it has no reserve of pronation available. Bankart and Blundell [4] affirmed Lovett and Cotton’s idea when they stated, “People do not suffer from flat foot, but from inability to flatten their feet.” Wiles [5] (p1089) also tried to give a more specific definition of the flat foot when he wrote:

A flat foot is one which is structurally built so as to have a low arch when the foot is in the ideal posture for that individual ... it must be carefully distinguished from the pathological condition with an everted, abducted foot which is usually called ‘flat-foot.’ ... In [the latter] cases the arch ... is lost because of a complicated rotation in which the forefoot is everted (pronated) and abducted.

The work of Root [6] on the classification of foot types and treatment of various foot types still had a basis in Lovett and Cotton’s and Wiles’ definitions. Every author over the past 100 years has repeated the assertion that the actual height of the arch has almost no relationship to symptomatology. Thus practitioners are in the same quandary today as they were in 1888: On what basis does one decide which feet will become symptomatic and which ones will not? Regardless of Staheli’s contention that “new” research has given us a more complete understanding of the normal foot—and I have read every paper cited by Staheli in his article—there is little that compares symptomatic and asymptomatic feet and tries to distinguish between them.

3) I cannot accept Staheli’s definition of a “normal” arch as one that is within two standard deviations of the average. Such a concept of “normal” is not used in other areas of medicine: It does not divide those who have satisfactory vision from those who do not; it does not distinguish the diabetic from the nondiabetic; it does not separate the hypertensive population from the normotensive population. Why, then, should it be used to divide the population with normal arch function from the population with abnormal arch function? Using this criterion, one would have to conclude that only 5% of the population would complain of a musculoskeletal problem associated with the arches. Gould et al [7] showed, in a survey of the shoe-buying public, that as many as 74 million people in the United States may have foot problems. One need only look at a classic article such as that of Barnicot and Hardy [8] on hallux valgus or that of Dunn [9] on arch mechan-ics to see that there is a great deal of overlap in terms of standard deviations for those who are normal and those who are abnormal. Many others have found similar results [10,11]. I would like to recommend a return to the definition of the normal foot provided by Root et al [12] (p24):

a set of circumstances whereby the foot will function in a manner which will not create adverse physical or emotional response in the individual. This . . . applies when the lower extremity is used in an average manner an in an average environment, as dictated by the needs of society at the moment.

Such a definition validates the statement by Staheli that one may be beyond two standard deviations of the mean and still be normal. It also supports the concept that one may be within two standard deviations of the mean and yet be abnormal.

4) The classification system offered in Staheli’s article seems to be little more than a reiteration of the classification scheme proposed by Barry and Scranton [13]. Their classification system is based more on the opinions of earlier authors than on an actual analysis of the foot morphologies and the forces that result in flatfoot. Kitaoka et al. [14,15] have done extensive work to discover what makes the foot become flat; none of this work is referenced by Staheli. The alignment factors involving the forefoot and the rearfoot should also be considered [16,17]. The definition of joint axes and deviations of those joint axes from the average is certainly not considered [18]. In my opinion, “flatfoot” must be evaluated not from the perspective of what the foot looks like, but from the standpoint of what forces are responsible for its flattening, and what resultant movements and stresses are imparted as a result of that flattening. It has already been demonstrated that joint axes exhibit wide variations, which may partly explain why some pronated feet give rise to symptoms and some do not [19,20,21].

5) The role of shoe wearing has always been controversial. Beginning with the work of Hoff-man [22] in the early part of the century, it has been argued that populations that tend to go barefoot have fewer foot problems than those in which shoes are usually worn. Sachithanandam and Joseph [23] showed that the prevalence of flatfoot in a sample of people who delayed shoe wearing until skeletal maturity was reached was only 1.75%, as compared with 3.25% for those who did not delay shoe wearing. On the other hand, a study by Alakija [24] comparing children who wore shoes and those who did not showed just the opposite, that shoe wearing reduced the prevalence of flatfoot from 6.9% to 1.9%. Again, it may be that for certain foot types shoes help the foot develop properly, while for other foot types, shoes retard arch development. Regardless of the results of any such research, the wearing of shoes by children who attend school in most areas of the United States is not optional. Thus it is a huge waste of time and energy to argue that children in the United States, especially school-aged children, should not wear shoes for most of the day.

6) Staheli states that patients with physiologic flatfoot have radiographic results that fall within normal limits. This is a very confusing statement. There is no indication in this article of whose values the author considers to be “normal,” nor is the reader referred to any research that would provide support for this statement. Does Staheli agree with Bleck and Berzins [25] that the talar declination angle should not be considered to be abnormal unless it is greater than 25°? Does he agree with the view that on the lateral view the talar bisection line should fall through the bisector of the first metatarsal? [26,27,28] Does he agree with Saltzman et al. [29] that the lateral calcaneometatarsal angle should be 132°? Does he agree with Stewart [30] that the radiographic parameters for normalcy must be based on ethnicity? It has been demonstrated that the actual arch height as shown radiographically may have little relation to an examiner’s clinical assessment of the arch height as “normal” or “abnormal.” [31,32]. However, most of the above-referenced authors have indicated that the diagnosis of flatfoot should be based on radiographic evidence. Isikan [33] demon-strated that there are radiographic differences between the patient with and the patient without painful pes planus. There is also evidence that there may indeed be an optimal calcaneal inclination angle, deviations from which in either direction may result in loss of efficiency [34].

7) I agree with Staheli that, on average, arch height does increase as a child matures. The aggregate statistics provided by Staheli et al. [1] are indeed impressive and useful. However, it is clear that there are many people in whom arch height does not increase during childhood, as substantiated by reports on the efficacy of shoe inserts [25,35,36]. The assumption, then, that the arch height will increase as a child grows is just as invalid as the assumption that it will not. In addition, it should be pointed out that no one to date has studied how subtalar joint position changes during childhood. It is widely recognized that the actual height of the arch or the degree of valgus of the heel has very little to do with whether the person is standing with the subtalar joint in a fully pronated position. That is why Root rejected the definition of Wright et al. [37] of subtalar joint neutral as a position in which the heel is vertical—he recognized that there are many people walking around with a vertical heel and a fully pronated subtalar joint. Does the fact that a child’s arch is increasing in height as he or she gets older mean that the subtalar joint is moving from a more pronated to a less pronated position? No published research to date has addressed this issue.

A common misconception in the medical community is that in cases of flatfoot, what is being treated, or what should be treated, is actual arch height. Yet there are many pronated feet that have completely normal or even high arches. What Staheli fails to acknowledge is that proponents of orthotic therapy in children are not necessarily trying to “correct” a flat arch but are trying to keep the subtalar and midtarsal joints functioning in the middle of their range of motion, providing a reserve of pronation that may be used as needed. Evidence is beginning to accumulate that changes in lower-extremity mechanics may be effected by the use of orthotic shoe inlays [38,39,40,41]. In the mind of every practitioner who treats children, in every individual case, is the question of whether a positive change in function may be beneficial to the child emotionally and physically. Speaking for myself, the large number of children I have treated over the years who have chosen to wear their orthoses because they feel better with them than without them has done more to convince me that many children need treatment than all the research articles ever published.

To be sure, there is still much controversy over whether children’s feet can be altered through the use of orthotic devices placed in the shoes. Mereday et al. [42], Bleck and Berzins [25], Bleck [26], and Bordelon [28] give credence to the idea that a positive change can be effected, whereas Wenger et al. [36] showed that no change was effected. Penneau et al. [43] used some very confusing reasoning in first presenting statistics indicating that they effected a positive change in the radiographic measurements of most of the children they treated, and then concluding that there was no change. I am still trying to find a statistician who can explain their statements. Kilmartin et al. [44] showed a slight negative change in the feet of children who wore orthoses. In trying to decipher the literature and come to a final conclusion, one cannot help noticing that the methodologies of the various authors for the manufacture of orthoses differ. For example, Bordelon [28] used a nonweight-bearing mold of the foot, whereas Wenger et al. [36] used a standard weightbearing mold. It is not surprising that the use of different methodologies in the manufacture of orthoses may result in very different outcomes. What this should tell the practitioner is that the manufacture and prescription of orthoses involve many variables, and that the use of these devices should be approached with the same care as is given to surgical procedures.

Staheli’s article is very useful in proposing ideas that may find both supporters and detractors in the podiatric community. I encourage all practitioners to study the references cited in Staheli’s article in order to discover the stengths and weaknesses of the research that has been published. The result can only be more and better research on this topic at educational institutions as well as at public and private podiatric clinics and offices throughout the country.